In recent years, it has become very popular to add bath salts or bath balls to a bath. Generally, such bath salt and bath ball compositions contain an inorganic salt mixture comprising sodium sulfate, borax, sulfur, sodium chloride or a carbonate salt, together with perfume, colourant and plant extract. The purpose of the salts or balls is to provide the bath with perfume and/or colour, to improve the aesthetics of the bath and at the same time create a stimulating effect on the skin. In the case of effervescing salt compositions, they usually comprise a combination of a carbonate salt and an acid which when dissolved in the bath, produce carbon dioxide gas bubbles which provide a relaxing and refreshing sensation to the bath. In the case of foaming bath salts or balls, a surfactant is included.
Several U.S. patents disclose bath salt or bath ball compositions. U.S. Pat. No. 4,666,707, Eguchi et al., assigned to Kao Corporation, granted May 19, 1987, discloses a weakly acidic effervescing bath salt composition which contains a carbonate salt and an acid which gives the bath a weakly acidic character. The carbonate salt that is incorporated in the weakly acidic bath salt composition can be sodium hydrogen carbonate, sodium carbonate, sodium sesquicarbonate, potassium hydrogen carbonate, potassium carbonate, potassium sesquicarbonate, ammonium hydrogen carbonate, ammonium carbonate and ammonium sesquicarbonate. These salts may be used either alone or in combination with one another. The weakly acidic nature of the bath purportedly enhances retention of carbon dioxide gas in the bath which purportedly promotes blood circulation and prevents a chill after bathing. The composition also incorporates a moisturizer which allegedly leads to a synergistic increase in blood circulation and enhances moisture in the skin.
The acid contained in the weakly acidic bath salt composition purportedly can be an organic acid such as formic acid, a straight chain aliphatic acid, for example, acetic acid, propionic acid, butyric acid or valeric acid; dicarboxylic acid such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelio acid, fumaric acid, maleic acid, phthalic acid, isophthalic acid and terephthalic acid; acidic amino acids such as glutamic acid and aspartic acid; hydroxy acids such as glycolic acid, lactic acid, hydroxyacrylic acid, .alpha.-hydroxybutyric acid, glyceric acid, tartronic acid, malic acid, tartaric acid, hydroxybenzoic acid, citric acid, salicylic acid (o, m, p), gallic acid, mandelic acid, tropic acid, ascorbic acid and gluconic acid; cinnamic acid, benzoic acid, phenylacetic acid, nicotinic acid, kainic acid, sorbic acid, pyrrolidonecarboxylic acid, trimellitic acid, benzenesulfonic acid and toluenesulfonic acid; and acidic salts of these organic acids. The inorganic acids include, among others, phosphoric acid, potassium dihydrogen phosphate, sodium dihydrogen phosphate, sodium sulfite, potassium sulfite, sodium pyrosulfite (sodium metabisulfite), potassium pyrosulfite (potassium metabisulfite), acidic sodium hexametaphosphate, acidic potassium hexametaphosphate, acidic sodium pyrophosphate, acidic potassium pyrophosphate and sulfamic acid. Preferred acids are aliphatic dicarboxylic acids such as succinic acid, and fumaric acid and phosphoric acid as well as acidic salts of these.
Typical examples of the moisturizer that can purportedly be used in the composition are stated as follows:
(1) Organic acid salts such as sodium lactate, disodium tartrate, sodium pyrrolidonecarboxylate and disodium glutamate; PA1 (2) Polyhydric alcohols such as propylene glycol, 1,3-butylene glycol, glycerol and sorbitol; PA1 (3) Water-soluble macromolecules such as polyethylene glycol, polyvinyl alcohol, sodium alginate and polyvinylpyrrolidone; PA1 (4) Mucopolysaccharides such as chondroitin sulfate and hyaluronic acid; PA1 (5) Collagen and derivatives thereof; and PA1 (6) Nucleic acids (DNA, RNA), proteins such as elastin, keratin, fibroin, and hydrolyzates thereof. PA1 (a) sodium bicarbonate, 40 to 90% weight; PA1 (b) organic acid such as citric acid, 5 to 50% weight; and PA1 (c) alcohol such as ethyl alcohol, methyl alcohol, propyl alcohol or butyl alcohol, 0.5 to 15% weight. Preferably, the alcohol is hydrous. A preferred hydrous alcohol is hydrous ethanol with 5% water. PA1 (d) animal oil such as lanolin, mineral oil or vegetable oil such as canola oil (oil obtained from canola seed), safflower oil, sunflower seed oil, olive oil, corn oil, nut oil and fruit oil, and the like, 0.5 to 10% weight. PA1 (e) FD&C certified colours to import colour to the formulation; and PA1 (f) fragrance.
The ratio between the carbonate salt and the acid in the bath salt composition is stated to be such that when added to the bath, the bath salt composition renders the bath weakly acidic, namely such that a 0.01 weight percent aqueous solution of the bath salt composition has a pH of 4 to 7, preferably 6.0 to 6.7. When the pH is lower than 4, the stimulation to the skin is said to become severe while at the same time there is a risk of corrosively damaging the bath heater and the like. At a pH exceeding 7, it is stated that the carbon dioxide retention and blood circulation promotion effects of the composition cannot be produced.
According to the inventors, Eguchi et al., the effect of the invention is based on the principle that, on the acidic side of a pH of 7.0, carbon dioxide occurs as the CO.sub.2 molecule and produces the blood circulation promoting effect whereas on the alkaline side of a pH of 7.0, carbon dioxide occurs as the CO.sub.3.sup.2- or HCO.sub.3.sup.- ion, so that the blood circulation promoting effect cannot be produced. The proportion of carbonate salt to acid to satisfy the required conditions may vary depending on the kind of carbonate salt and of acid but, preferably, the carbonate salt allegedly accounts for 5 to 80% by weight, more preferably 10 to 50%, and the acid purportedly accounts for 10 to 80%, more preferably 15 to 50%, based on the whole composition. It is said that the moisturizer can be incorporated in an amount varying in a wide range. Generally, however, it is used in an amount of 0.001 to 10%, preferably 0.01 to 2%, on the whole composition basis.
Other effervescing bath preparations are also known. A fundamental preparation is disclosed in U.S. Pat. No. 4,650,667. A further example is a preparation which employs low-cost fumaric acid, and is available under the trademark AC-TIBATH.RTM., as well as other names.
U.S. Pat. No. 5,110,603, Rau, assigned to Kao Corporation, and the Andrew Jergens Company, granted May 5, 1992, discloses a colloidal material containing bath composition which, when the composition is dissolved in water, also generates carbon dioxide. The composition is physically bound together as a tablet with a colloidal material. The effervescence produced by dissolving the tablet in the water purportedly improves dispersion of the colloidal material, and maintains the colloidal material in suspension in the water for a longer period of time. The colloidal material is selected so as to provide relief from skin irritation. An acid, a carbonate salt, and a colloidal material such as colloidal oatmeal may be tableted to provide an effective, easily stored and handled product. Specifically, the bath composition is stated to comprise aggregated particles composed of (1) a composition which will dissolve in warm and hot water to release carbon dioxide, the composition comprising a carbonate salt and an acid. The carbonate salt and acid are intimately mixed with 0.1-50%, by weight, of a colloidal material suitable or treatment of skin. The colloidal material is selected from the group consisting of colloidal oatmeal, flour derived from corn, wheat, soy, rice or barley, meals obtained from corn or almond, hydrophobic starch obtained from corn, wheat, rice, potato, water-insoluble gums, cellulose and mixtures thereof.
The treatment of minor skin irritations, and in particular, relief from itching induced by inflammation, disease, trauma and the like, through the water-mediated application of colloidal materials is well known. Prominent among various materials of this type is colloidal oatmeal, commercially available under the mark AVEENO.RTM. from S.C. Johnson Company, as well as from other sources. Hydrophobic starches are also well known in this application as substances which, when dispersed in water, settle on and desensitize the skin, and provide temporary relief. In general, the colloidal material treatments are effected by dispersing the colloidal material in bath water, and then bathing in the bath suspension. This method presents a number of problems.
Maximum effectiveness is stated to be achieved by thorough dispersion of the colloidal material throughout the bath water, as these materials are generally in powder form. There is an inherent problem because thorough dispersion of the material tends to be frustrated by the tendency of such materials to swell, soften and agglomerature upon exposure to water. A further problem is that agglomerated particles of this type tend to settle relatively rapidly, thereby reducing shelf life and effectiveness in the bath. Yet a further problem is that, due to the colloidal nature of this material, it tends to persist in the tub or bathing enclosure even after the water is drained. The problem is compounded because the greater the degree of agglomeration, the more difficult it is to remove residual material.